Project Summary Infant obesity is increasing in the U.S., particularly among Hispanics. Rapid weight gain during critical periods of infancy increases the risk of obesity in childhood, continuing into adulthood and increasing the risk of chromic diseases such as diabetes and hypertension. This serious health threat could be prevented through multifaceted interventions during infancy that address multiple risk factors associated with early obesity development. Current evidence suggests that trials should focus particularly on risk factors related to physical activity, sleep, nutrition, satiety, stress and increasing parenting skills, and should be delivered at multiple levels, using population-level programs to be translatable, cost-effective and sustainable. To this end, interventions carried out within the federal WIC program provide a potentially powerful way of fostering early healthy behaviors and helping in preventing obesity. Successful interventions done as part of the WIC program could be translated into their policies, since each state develops its own educational materials and determines how nutritional education is implemented. Our goal is to test the clinical effectiveness of a multi-faceted and multi-leveled intervention focusing on three main areas: physical activity (i.e., infant activation, sleep and screen time), nutrition and growth monitoring, framed in the Health Self-Empowerment Theory, and delivered through the WIC Program using a multi-media approach. The physical activity and growth-monitoring components are new to the WIC curriculum, while the nutrition component is based on WIC guidelines but delivered differently (through self- empowerment-based messages and multi-media based). For this, we will conduct a cluster-randomized controlled trial among pregnant women participants of the Puerto Rico WIC (PR-WIC) program. An equal number of clinics will be randomized to the control (usual care) arm or to the WIC+ (usual care + intervention) arm in the San Juan area. The lifestyle intervention will focus on age-appropriate infant physical activation, healthy sleep and limiting screen time, healthy dietary patterns and growth monitoring. The content will be delivered with a multi-media approach (web-platform, mobile messages and phone follow-up). Participation in the intervention will begin in the last trimester of pregnancy and continue until the infant is 12 months old. We have already pilot-tested the information of this intervention among 10 mother-infant dyads during their first year of life, with excellent acceptability. We will determine the extent to which the intervention may impact adequate weight gain, infant activity and nutrition from birth to 12 months of age compared to the control arm. We will also evaluate the cost of this intervention as a modification of the current WIC curriculum. Such approach has not been tested before among infants. If successful, this intervention could be adopted as a policy-supported best practice by the PR-WIC program to help prevent infant obesity. This will help improve minority health and eliminate health disparities among Hispanics and other at-risk groups.